This disclosure relates to a movement simulator, comprising a base; a platform movable relative to said base; actuators having a controllable length, said actuators being coupled with said base and carrying said platform, wherein the dimensions of the base, platform and the variable lengths of the actuators determine a workspace within which the platform can move; and a controller operable to provide a motion cueing algorithm having a demanded state as output and a washout controller having a washout adaptation as output, which washout controller keeps the platform within its workspace by adapting the demanded state to a commanded state using the washout adaptation, wherein the commanded state controls the length of the actuators.
An example of such an apparatus that is most commonly used for movement simulators is the so-called Stewart platform which comprises a fixed base, moving platform and 6 actuators. An example of such a Stuart Platform is described in EP-A-446786. A Stewart Platform is a kind of parallel manipulator using an octahedral assembly of struts. A Stewart platform has six degrees of freedom (x, y, z, pitch, roll, & yaw), also referred to as the platform domain coordinates. There are six independently actuated elements or legs, where the lengths of the legs are changed to position and orient the platform. The status of the platform can also be expressed by the actual length of the legs. This is referred to as the so-called actuator domain and is different from the platform domain coordinates.
Many movement simulators have been developed for many different types of vehicles. In order to make a simulation more realistic, linear accelerations and angular rates are exerted on the user by moving the platform. This activity is also referred to as motion cueing. The movement of the simulator is controlled by a so-called motion cueing algorithm. These platform movements however should not drive the simulator out of its workspace. The software component that is in charge of keeping the simulator platform within its workspace is commonly referred to as a washout filter. The washout filter aims to bring the platform back into a substantially central position whereby the forces exerted on the user are minimal. Thus the user preferably does not experience the lower-frequency washout movement of the platform to its central position as opposed to the high frequency movements caused by the motion cueing algorithm.
US-A-2009/0047636 describes a method for controlling the movements of a flight simulator, wherein a 2nd order high pass filter and a conventional 1st order washout filter are used. Such a washout filter will act irrespective of the actual position of the platform. This results in that the washout filter will also act when the platform itself is not far away from its central position and therefore no washout action is actually required.